It is known to monitor physiological parameters of subjects in medical and safety environments. Whilst several products are available which aim to continuously increase the level of relaxation of the user (for example, RESPeRATE®, StressEraser) there are many situations (such as operating dangerous machinery) where it could be dangerous to be too relaxed as this could result in the user falling asleep, or moving towards a dangerously low level of alertness. This (hypo-vigilance) is a known issue and there are approaches to prevent this happening (see for example the project “AWAKE”, European project IST-2000-28062, http://www.awake-eu.org/objectives.html) However, in still more circumstances in general situations where people are interacting not just with machinery but also with other people (for example when driving, at work, aircraft pilots, train drivers, shop assistants or counter workers in banks, local council, call centre personnel etc.), it is important not only to stay alert (i.e. to limit the amount of relaxation, as described above) but also to avoid becoming too stressed or too aroused, as this will also limit the ability of the individual to function optimally.
The system referred to above as “RESPeRATE®” (see for example the website http://www.resperate.com/) is a portable electronic device that helps a subject lower their blood pressure and stress levels naturally by device-guided breathing. The device uses the body's natural tendency to follow external rhythms interactively guiding the user to reduce their breathing rate to a “therapeutic zone” of less than 10 breaths per minute. This system is the only medical device clinically proven to lower blood pressure through paced breathing therapy and is available for sale without a prescription (over-the-counter—OTC). Another product which operates to reduce stress in patients is the StressEraser (see for example United States Patent Application Publication US 2005/0288601). Both of these products aim to continuously reduce stress levels and as such provide no facility to limit the lower level of stress—indeed when using both products it may be pleasant for the user to fall asleep.
However, in certain cases (such as operating dangerous machinery) it is not desirable for a subject to fall asleep: it could be dangerous to be too relaxed as this could result in the user falling asleep. This is known from the European project “AWAKE” mentioned above. One purpose of this project is to provide a system that prevents a vehicle driver from falling asleep. In such a case of hypo-vigilance the system will provide an adequate warning to the driver with various levels of warnings, according to the estimated driver's hypo-vigilance state and also to the actual traffic environment. This system will operate reliably and effectively in all highway scenarios.
A similar system known as the “Driver Warning System” also referred to as “DWS” can use acoustic, visual and haptic means according to the type of AWAKE warning. Acoustic warnings include different warning tones to raise the driver's alertness and speech messages to indicate why the warning has been activated. Visual elements of the alarm are either located at the rear view mirror for the demo cars or at an external box on top of the dashboard of the truck demonstrator. These devices also host a smart card reader and the On/Off button of the system. The haptic warning is based on a vibration device attached to the seat belt lock. The vibrations stimulus can be felt all along the seat belt.
There does not exist, however, a system that can monitor the state of a subject and respond to the subject in order to maintain a specific state in the subject, without that subject becoming either too aroused or too relaxed.